Question

If you were to use the elimination method to solve the following system, choose the new system of equations that would result after the variable z is eliminated in the first and second equations, then the second and third equations.

x - 3y - 3z = -13
x + 2y - z = -1
2x + 3y + 2z = 0

How do I do this and what do you get for an answer?

Answer 1

multiply equation 2 by 2:
2x + 4y - 2z = -2 add to no. 3
2x + 3y + 2z = 0
4x + 7y = -2......................(1)
multiply second by 3
3x + 6y - 3z = -3 subtract first equation from this one
x - 3y - 3z = -13
2x + 9y = 10.......................(2)
multiply (2) by 2
4x + 18y = 20
subtract the above from (1):
-11y = -22
y = 2
substitute y = 2 in equation (2):
2x + 18 = 10
x = -4

now substitute for x and y in first of original equatios
x - 3y - 3z = -13
-4 - 6 - 3z = -13
3z = 3
z = 1
so x = -4,y=2, z = 1

check results in 3rd equation:
2(-4) + 3(2) + 2(1) = 0


ok

Answer 2

phew!! - i'm a little tired!!

Answer 3

is that what you wanted?

Answer 4

Yep :] Thanks! Haha.